Railguns haven't progressed to a combat-capable level of technology yet. The rails wear out too fast, and nobody (to my knowledge) is working on designing railguns intended for large volumes of fire. There are naval cannon designs in the works, but they wear out pretty fast. With an A-10, you'd want the barrels to last (at a bare minimum) thousands of rounds so that even in a high ops tempo situation you could go a month without replacing them.

Most railguns are good for ten rounds before the rails need replaced. And that is including a decrease in efficiency towards the end of that ten rounds, due to the current melting the rails and increasing the effective resistance of the armature.

Also, keep in mind that a railgun is a single-purpose weapon. It'd would be like arming a tank with only APFSDS rounds instead of a mix of APFSDS, HEAP, and cannister rounds. That railgun round will do an ungodly amount of damage to a single target, but it's not going to do much to a squad of infantry riding in a 7-ton truck. Oh, there'd be a lovely hole, and anyone that got hit would be amazingly fucked, but there's no way to stick an explosive round inside a railgun.

By necessity (and I mean "laws of EM physics") all railgun projectiles need to be non-ferrous and able to handle insane amounts of current. I did a fair bit of research into this a while back, throwing a 1-kilo projo with a diameter of an inch (for a long, high-BC dart) came out to something like 187,000 amps running through the projo, and that's just to get past the sound barrier with a 2-meter rail setup.

To actually break through a tank's armor, you're going to need a lot more than 1-kg copper dart. For metals, you absolutely cannot use anything has generates a magnetic field. While it's true that anything can be armor-piercing if it's moving fast enough, for practical reasons harder metals are better, and occasionally have fun properties like being pyrophoric on impact.

Also, to generate enough current fast enough, a bank of supercapacitors needs to be used, and those need to be built in a fairly specialized way to prevent the magnetic fields generated by the current in the wires, cables, and capacitors themselves from literally tearing themselves apart. I've seen videos of railguns firing where the capacitor bank tore itself apart, which is of course absolutely unacceptable inside a flying plane.

>>7170wouldn't fix the other problems, but what about using a pair of compulsators instead of capacitor banks? From what I heard, compulsators are supposed to be pretty awesome for applications like railguns, and you could probably power them from the plane's engines. It would HAVE to be 2 (or other even numbers) rotating in opposite directions or else you run into unpleasant issues.

>>7178J = (kg*(m/s)^2)/2
Speed of sound is anywhere from 320m/s to 355m/s in normal temperature ranges.
Assuming a nice 20c(68f), we get the 343m/s quoted above, that puts mach 3 at 1029m/s, using a copper slug that is 10cc*(8.95g/cc) we get (.0895*1029^2)/2=47383J or about 47kJ.
J = W/s
So 2.3m/1029m/s = 0.002235s
That's not really right, because acceleration means it's a little slower, but this gives us worst case.
47383J/0.002235s = 21200447W or about 21.2MW divided by whatever your efficiency is.

>>7179Longer is always better, just like that sexy PTRD you've got, because one can utilize a slower acceleration, but there's always a practical consideration. The total length of the GAU-8 system is around 5 meters, but the entire airframe would have to be redesigned to handle a very different stress load.

Railguns efficiency, and the formulae required to figure out how much current is required to accelerate a given mass at to a given speed, depends a lot on design.

The width between the rails is one factor, the inductance caused by the current in the rails, material composition of both rails and projo, and whether or not the design uses plasma to push the projo (or not) are others.

>>7551Increased weight not only of gun but ammunition carriage and loading system (the gun by itself is almost twice the weight of the GAU-8 due to the increase in caliber), not enough room for recoil compensation mechanism in the airframe because that revolver cannon uses a recoiling barrel mechanism, changing the location of the feed mechanism requires rework of the internal structure of the airframe, increased power requirements vs. rotating barrel assembly motor due to larger components, reduced magazine capacity as the 35x228 mm round is much larger than 30x173mm fired by the GAU 8. Range increase is useless because of the nature of CAS cannon use; you can't shoot if you cannot see and identify the target, and without some kind of complex zoom-capable scope or camera system also installed and slaved to the gun, you can't see to distinguish targets at the longer range of the Rheinmetall canon anyway.

Really, ammunition size is the biggest reason. You'd have to lengthen the airframe by 3 or 4 feet just to accept the ammunition size increase and associated storage system changes while still reducing ammo load by over 60%, before any other changes are made. Pic related. Blue tip is 30x173 currently fired by the A-10, far right is 35x228 round fired by the revolver cannon in your vid.

Although I take some issue with the weight, you're comparing bare guns. The GAU-8 has associated electric and hydraulic systems which aren't included in the overall weight. Moreover the electric and hydraulic system is DOUBLED for redundancy sake.
The 35mm revolver cannon is by comparison gas driven and self contained. It has no power requirements from the engines or any other system, so its much more robust, reliable, and probably lighter all things considered.

The first sort of salient argument is the ammunition allotment, but you forgot to mention the rate of fire is 3x less, so a two third reduction in ammo is going to result in roughly the same fire time at a longer range (or better penetration at same range).
The second sort of salient argument is something you didn't mention, which is the mass delivered (550g for 35mm vs 1164g for 30mm). Although that ignores accuracy, which is undoubtedly better for the 35mm gun.

I still say an airframe 5 feet longer and with actual long range FCS system mounting the 35mm cannon is far more realistic than anything else mentioned in the thread.

>>7553>Although I take some issue with the weight, you're comparing bare guns. The GAU-8 has associated electric and hydraulic systems which aren't included in the overall weight. Moreover the electric and hydraulic system is DOUBLED for redundancy sake.
The 35mm revolver cannon is by comparison gas driven and self contained. It has no power requirements from the engines or any other system, so its much more robust, reliable, and probably lighter all things considered.

https://en.wikipedia.org/wiki/Rheinmetall_Oerlikon_Millennium_Gun>WeightGun: 450 kg
>A Millennium gun and 252 rounds weighs 3,200 kg.
>The Millennium gun is easy to install as it requires no through deck penetration and needs no supply of coolant, air or ship's power to operate. However, it does need a power supply to recharge its batteries.

There's no weight savings at all in the gun and ammunition storage by switching to the 35mm gun. It actually doubles the weight. And it's still going to need some kind of powered feed mechanism because it's go to load against g-forces and in positions and angles of attack that a naval gun won't ever see.

There's also the fact that the Millennium gun essentially fires canister rounds.
>A device at the muzzle end of the barrel measures the exact speed of each round as it is fired, and automatically sets the fuse to detonate the round as it approaches a pre-set distance from the target. Each round disperses 152 small tungsten projectiles to strike the incoming target.

So... your whole weight of projectile argument is invalidated until they develop a solid projectile for it. And the accuracy argument, because it's just shotgunning with less-effective tungsten ball bearings. Great for anti-ship missiles, aircraft, infantry and light vehicles, not so great for penetrating anything approaching IFV armor or better. Couldn't even kill a T-72, which at least the GAU-8 can.

And then the ammo capacity reduction. I was just guessing on the 60% reduction. Even if that is correct, the A-10 carries 1350 rounds MAX, generally 1174. That gives it 11 seconds of continuous fire. 60% reduction, that'd give the Millennium gun ~700 rounds. At a 1000rpm rate of fire, thats still only 7 seconds. Of tungsten canister rounds. And as the Millennium gun weighs 450Kg, and it with 252 rounds weighs 3200kg, that means that a 252 round ammo load weighs 1750kg. Triple that for an effective A-10 combat load (again, with the lighter weight canister rounds!) and thats 5250 kg in ammo weight alone.

>>7554Like I said there are lighter options using 35x228 if you're worried about weight.

Some corrections:
1. There is a 35x228mm APDS fired at 1440m/s.
2. Gau-8 fits 1174 rounds max, 1150 in general use.
3. It's 17.6 seconds of fire for the GAU-8, 42 seconds of fire for the 35mm on 700 round drum. 295 rounds of 35mm are going to be spent about as fast as 1550 rounds of 30mm.
4. 252 rounds of 35mm does not weigh almost two tons, a single round of 35mm would have to weigh 6.9kg for that. Your 3200kg claim is incorrect, wiki may be talking about the naval turret mount not the actual gun.

>>7555>1. There is a 35x228mm APDS fired at 1440m/s
Didn't know that. can't find any pages with info on the system other than Wikipedia. it seems Rheinmetall took down their own page with specs.

>2. Gau-8 fits 1174 rounds max, 1150 in general use.
I've always heard the 1,350 was max, but because of the way the magazine stores empty casings the air force directed it not be filled to max capacity. Again, can't find anything but random sites or wikipedia with exact information.

>3. It's 17.6 seconds of fire for the GAU-8, 42 seconds of fire for the 35mm on 700 round drum. 295 rounds of 35mm are going to be spent about as fast as 1550 rounds of 30mm.
Yeah, my math is fucked. Thats what I get for trying to think during the Super Bowl.

>4. 252 rounds of 35mm does not weigh almost two tons, a single round of 35mm would have to weigh 6.9kg for that. Your 3200kg claim is incorrect, wiki may be talking about the naval turret mount not the actual gun.
Don't know. All I have is wikipedia's specs that the turret alone weighs 3300kg, the gun 450, and Gun+ammo is 3200.

>>7554> It has no power requirements from the engines or any other system, so its much more robust, reliable, and probably lighter all things considered.

I disagree with this point. Externally powered guns are reliable as hell because they're completely unaffected by ammo variations. It's like a pump action vs a semi-auto shotgun, except you've got the Terminator running the pump.

> The chain gun operating principle is inherently reliable. An unclassified report on the EX-34 prepared by the Naval Surface Weapons Center in Dahlgren, Virginia, dated September 23, 1983, said that:

> 29,721 rounds of endurance tests were fired with no parts breakage and without any gun stoppages . . . It is significant that during firing of 101,343 rounds not one jam or stoppage occurred due to loss of round control in the gun or feeder mechanism . . . [this] is in our experience very unusual in any weapon of any caliber or type.

Hydraulic pumps/motors and electric motors are plenty reliable. And if you don't have power from the engines, well you probably don't care about the gun at that point.

>>7560> You're talking about how many rounds can be fired through it without stopping, which isn't an important reliability factor for an aircraft.

I was talking about what happens when you have an ammo problem. A gas or recoil powered gun needs to be cycled by some external force. (Vid related.) An externally powered gun already does that.

> Reliability vis a vis fewer parts means that when it DOES break, there's less parts to requisition to fix it. Also it's fewer crucial components that can be damaged by enemy fire.

Aircraft are high maintenance machines and the military has plenty of spare parts. Also the gun is not a crucial component. If an engine / hydraulic pump / generator gets knocked out, the mission is over and it's time to RTB.

I'm not saying a revolver cannon is a bad idea, just that external power is the way to go.

However, gatling guns are fucking awesome, and not that much heavier than revolver cannons. The 27mm Mauser BK-27 gas powered revolver cannons weighs 220lbs, while the GAU-12 25mm rotary cannon weighs 270 lbs, with double the rate of fire.

>needs to be cycled
Why does it need to be cycled? Is the enemy coming over the hill? It's an airplane, if ordnance malfunctions you let your wingman do the job and RTB for fixing.
If you're that worried, it's possible to use a blank cartridge system to clear it like the Russians do.

I like revolver cannon because for a given caliber it will be lighter and more accurate, while offering comparable rates of fire.

Imagine how much 35x228mm gatling cannon would weigh. 7 more barrels, plus an electric/hydraulic system, and a second electric/hydraulic system as a spare.

>>7567>Imagine how much 35x228mm gatling cannon would weigh. 7 more barrels, plus an electric/hydraulic system, and a second electric/hydraulic system as a spare.

You wouldn't need to have 7 barrels. 7 is just what they needed to reach the cyclic rate of 4,200 rpm and give each barrel enough time to cool on the GAU-8. If the designers wanted to go for a lower rate of fire, say 1800-2500, a 3 or 4 barrel configuration would work.

Its not impossible to make a lightweight gatling gun over 7.62x51mm caliber. The AH-1F Cobra onwards mount a three-barrel 20mm gun, the General Dynamics M197. 750 round magazine, 1500 RPM rate of fire.
https://en.wikipedia.org/wiki/M197_electric_cannon